﻿The genus Platydracus Thomson in Hainan, South China (Coleoptera, Staphylinidae, Staphylininae)

﻿Abstract A study on Platydracus species of Hainan Province, China is presented. Platydracushainanensissp. nov., Platydracusaureolussp. nov. and Platydracuszhouchenglinisp. nov. are described as new species. Platydracusmarmorellus Fauvel, 1895 and Platydracussubirideus Kraatz, 1859 are recorded from China for the first time. Habitus and diagnostic characters of all species are photographed, and a key to Platydracus species of Hainan is provided.


Introduction
Platydracus Thomson, 1858 is the largest genus among the subtribe Staphylinina Latreille, 1802.Up to the present, around 300 species have been described in the genus and 32 of them are known from China.Hainan is a large island located in the South China with high insect diversity.Yet only one species, Platydracus juang Smetana, 2005, has been presently recorded in this area (Zhou et al. 2024).After conducting several field investigations in Hainan, many staphylinid specimens were collected.Among them, six Platydracus species are recognized, including three new species which will be described in this paper.

Materials and methods
The specimens examined in this paper were collected by searching dead wood, sifting leaf litter and setting flight interception traps (FIT).For examination of the genitalia, the last three abdominal segments were detached from the body after softening in hot water.The aedeagus or tergite X, together with other dissected pieces, were mounted in Euparal (Chroma Gesellschaft Schmidt, Koengen, Germany) on plastic slides.Photos of sexual characters were taken with a Canon G9 camera attached to an Olympus SZX 16 stereomicroscope; habitus photos were taken with a Canon MP-E 65 mm macro lens attached to a Canon EOS7D camera and stacked with Zerene Stacker.The specimens treated in this study are deposited in the Department of Biology, Shanghai Normal University, P. R.China (SHNU), Natural History Museum of Denmark at the University of Copenhagen, Denmark (NHMD), the Canadian National Collection of Insects, Arachnids and Nematodes, Ontario, Canada (CNC) and the National Museum Prague, Czech Republic (NMPC).

Key to Platydracus species of Hainan
Diagnosis.The species is widely distributed in South China, and its detailed distributional information will be listed in a forthcoming paper by Qing-Hao Zhao.In general appearance, the species is similar to P. plagiicollis (Fairmaire, 1891) which overlaps in distribution.Yet, P. marmorellus can be easily distinguished from the latter by bearing pale appressed microsetae on the forebody, which are absent in P. plagiicollis.
Distribution.China (Hainan), Myanmar, Vietnam, Indonesia.New to China.Diagnosis.The species is similar to P. brachycerus Smetana & Davies, 2000, in most aspects, but it can be distinguished from the latter by the more rounded temples, longer pronotum, and sparser punctation of the head.

Platydracus juang
Distribution.China (Anhui, Fujian, Guangdong, Guangxi, Hainan, Hunan, Jiangxi, Taiwan, Zhejiang).Diagnosis.The new species belongs to the Platydracus brachycerus group, and it is similar to P. smetanai Zhou, Zhao & Tang, 2024 by sharing dense punctation of the head and short protarsomere 5. Yet, it can be distinguished from the latter by the distinctly larger body size (11.6-13.7 mm in P. smetanai) and a different aedeagus.
Body black, elytra with distinct copper tint, abdominal segments partially brownish, maxillary palpi, labial palpi and tarsomeres brownish with apical margin of each segment lighter, antennae dark brown with antennomeres gradually lighter apicad.
Head 1.30-1.37times as wide as long; eyes moderately large, tempora 1.18-1.27times as long as eye; surface with punctation dense and coarse; anterior portion of frons impunctate; pubescence most brownish except that behind anterior margin and eyes silver; antennomeres 1-3 distinctly longer than wide, antennomere 4 as long as wide, antennomeres 5-10 distinctly transverse, gradually incrassate, segments 4 to 11 covered with dense pubescence; maxillary palpi stout with last segment narrowly subtruncate apically; mandibles robust, inner edge of left mandible with two teeth on upper plane and mid tooth on lower plane, inner edge of right mandible with blunt anterior tooth and sharp posterior tooth on upper plane and mid tooth on lower plane.
Pronotum 1.00-1.03times as long as wide; disc with narrow impunctate midline, punctation distinctly sparser than that of head, pubescence brownish; scutellum with dense rugulose punctation and dark pubescence.
Elytra 0.98-1.02times as long as wide, punctation dense and coarse, pubescence behind humeri, along suture and posterior elytral margin silver, pubescence of the rest parts brownish.
Anterior legs with tibiae and tarsomeres distinctly stouter than those of the related species, tarsomere 5 rather short.
Abdominal tergites III-VI with basal transverse depression, with punctures coarser at base, gradually become finer apicad; pubescence brownish except for that of lateral portion of tergite III which is silver.
Male.Abdominal sternite VII with large median depression bearing numerous long dark brown setae; sternite VIII with posterior margin shallowly emarginate in the middle; aedeagus (Figs 15,16) almost symmetrical, median lobe  Diagnosis.The new species can be easily recognized from other Chinese species by larger body size and distinct coloration.
Body mostly black, except head and pronotum with strong golden tint on dorsal side, elytra light reddish-brown with several small dark marks, maxillary palpi, labial palpi and mandibles partially reddish-brown, legs reddish-brown, except for the trochanters, basal profemora and basal mesofemora blackish, tibial spurs dark brown, tarsomeres especially terminal segment more or less dark.
Head 1.29-1.32times as wide as long, eyes large, tempora 0.75-0.78times as long as eye; surface with punctation dense and umbilicate; pubescence mostly golden; antennomeres 1-3 distinctly longer than wide, antennomere 4 as long as wide, antennomeres 5-10 distinctly transverse, gradually incrassate, segments 4 to 11 covered with dense pubescence; maxillary palpi slender; mandibles relatively slender, inner edge of left mandible with two small teeth and two teeth on lower plane, inner edge of right mandible with small tooth on upper plane and small tooth on lower plane.
Pronotum 0.95-1.00times as long as wide; punctation similar to that of head, pubescence golden, relatively longer and more distinct than that of head; disc with small middle specular patch near posterior margin; scutellum with dense rugulose punctation and black pubescence.
Elytra 0.85-0.90times as long as wide, punctation fine and dense, pubescence mostly golden.Mesoventrite and metaventrite covered with golden pubescence laterally.
Body dark brown, pronotum reddish-brown along the margins, elytra reddish-brown with dark marks, maxillary palpi, labial palpi and mandibles reddish-brown, legs reddish-yellow, except for the trochanters and base of femora blackish, tibial spurs dark brown, tarsomeres more or less dark.
Head 1.24-1.40times as wide as long, eyes large, tempora 0.40-0.80times as long as eye; surface with punctation dense and umbilicate; pubescence mostly brownish; antennomeres 1-3 distinctly longer than wide, antennomere 4 slightly shorter than wide, antennomeres 5-10 distinctly transverse, gradually incrassate, segments 4 to 11 covered with dense pubescence; maxillary palpi slender; mandibles relatively slender, inner edge of left mandible with two acute teeth and two teeth on lower plane, inner edge of right mandible with round tooth and acute tooth on upper plane and acute tooth on lower plane.
Pronotum 1.03-1.08times as long as wide; punctation and pubescence similar to that of head; disc with narrow impunctate midline in posterior onefifth; scutellum with dense rugulose punctation and black pubescence.
Elytra 0.94-1.02times as long as wide, punctation fine and dense, pubescence comprised of two types of setae, long setae mostly brownish, short setae mostly whitish.
Abdomen with tergites densely punctate; tergites III-VII each with median golden tomentose patch and a pair of large dark tomentose spots, the lateral portions covered with long brown setae and short white setae, tergite VIII covered with golden pubescence which is distinctly sparse in apical third, tergite VII with apical palisade fringe.
Male.Abdominal sternite VIII with posterior margin emarginate in the middle; aedeagus (Figs 23,24) asymmetrical, twisted to right side in ventral view; median lobe with broad and round tip; paramere broad, with apical setae, subapical portion with cavity to accommodate apical tooth of the median lobe.
Etymology.This species is named in honor of Mr Cheng-Lin Zhou who collected many Platydracus specimens.